Analysis of external burning on inclined surfaces in supersonic flow

Abstract

An earlier analysis of a viscous mixing region with heat addition interacting with a supersonic external flow has been extended to include cases with a sloped wall beneath the viscous region. Also, cases with a supersonic to subsonic transition at the viscous throat have been studied for the first time. Limitations on the allowable heating value of the fuel that correspond to smooth subsonic to supersonic, or supersonic to subsonic transitions, are delineated and explained. The effects of wall slope at the throat and external Mach number on these limitations are shown. The results of calculations for representative cases show that it is possible to cancel base drag and even produce net thrust for cases with downward sloped walls if the initial Mach number in the viscous zone is supersonic prior to addition of heat. This corresponds to a supersonic to subsonic transition. For an initially subsonic flow, the results indicate pressures below the freestream static pressure throughout the flowfield. This means that only very limited drag from flameholders, such that the flow remains supersonic before heat addition, are advisable. Finally, some directions for future work are outlined.